This invention relates to the manufacture of integrated circuits and, more particularly, to controlling the onset of time-dependent haze during such manufacture.
Haze on mirror polished surfaces of silicon wafers has been attributed to the formation of SiO.sub.2 on the surface. It is postulated that H.sup.+ or OH.sup.- ions diffuse into the bulk of the wafer during aqueous cleaning steps. See, T. Shiraiwa et al, ASTM 960, pp. 313-323 (1986). These diffused species slowly leach out over time (e.g., during storage) and react with O.sub.2 or H.sub.2 O in the ambient to fore SiO.sub.2 particulates. The particulates scatter light, giving the appearance of haze. Consequently, the surface must be repolished to a specular state before the wafer can be utilized in the subsequent fabrication of integrated circuits.
Thus, a need remains in the integrated circuit art to control the onset of haze on silicon wafers so as to reduce the likelihood that the wafers have to be repolished, an extra process sequence which can be both expensive and time consuming.